Gas-phase basicities of the isomeric dihydroxybenzoic acids and gas-phase acidities of their radical cations
Gas-phase basicities of the isomeric dihydroxybenzoic acids and gas-phase acidities of their radical cations
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异构二羟基苯甲酸的气相碱度及其自由基阳离子的气相酸性
DOI：
10.1016/s1044-0305(00)00112-4
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发表时间：
2000
影响因子：
3.2
通讯作者：
D. Kuck
中科院分区：
文献类型：
--
作者：
Michael Mormann;S. Bashir;P. Derrick;D. Kuck
研究了六种二羟基苯甲酸（x，y-DHB）作为基质辅助激光解吸电离（MALDI）原型基质的热化学酸碱性质。六种DHB异构体的基态气相碱度（GB）和相应自由基阳离子（[x，y-DHB].+）的气相酸度（ΔG酸）已确定傅立叶变换离子回旋共振质谱采用热动力学方法。气相碱度从最低碱性异构体3，5-DHB的814 kJ mol− 1到最碱性异构体2，4-DHB的831 kJ mol− 1不等。得到的相应自由基阳离子的气相酸度从最酸性物质3，4-DHB的815 kJ mol− 1到最酸性物质2，5-DHB的858 kJ mol− 1不等。结果表明，基态质子转移从基质自由基阳离子的分析物可能发挥作用的电离过程中的MALDI，而质子转移从质子化的基质分子可以排除。
The thermochemical acid/base properties of the six dihydroxybenzoic acids (x, y-DHB) as prototypical matrices used in matrix-assisted laser desorption/ionization (MALDI) have been investigated. The ground-state gas-phase basicities (GB) of the six DHB isomers and the gas-phase acidities (ΔG acid) of the corresponding radical cations ([x, y-DHB].+) have been determined by Fourier-transform ion cyclotron resonance mass spectrometry employing the thermokinetic method. The gas-phase basicities vary from 814 kJ mol− 1 for the least basic isomer, 3, 5-DHB, to 831 kJ mol− 1 for the most basic isomer, 2, 4-DHB. The obtained gas-phase acidities of the corresponding radical cations vary from 815 kJ mol− 1 for the most acidic species, 3, 4-DHB, to 858 kJ mol− 1 for the least acidic one, 2, 5-DHB. The results indicate that ground-state proton transfer from the matrix radical cations to the analyte may play a role in the ionization process of MALDI, whereas proton transfer from protonated matrix molecules can be excluded.